Does any know the specs for wheel trueness? I've got a bit of a shake that doesn't seem to balance out, so I'm wondering if I have a wheel out of round or bent in some way. How much out of true will cause an issue on a 993? (It could also be my bushings I've got a set ready to install over the winter.)

How much side to side?
How much out of round?

 

Dan, I can't answer the Q about wheel runout, but what all have you inspected thus far? Jack up the front end and jiggle the wheels side-to-side and up-and-down. That will rule out the tie-rods or wheel bearings. Are your tires worn unevenly? Is it on one side only (can you tell)? Swap the front wheels left-to-right and see if it feels different.

There are a multitude of things it could be, including what you mention.

 

Are you doing a 'road force' balance where the tire is located in a specific position on the wheel? Also, all balance jobs are not equal. There are equipment differences as well as different skill/ability/desire levels of the techs doing the work. 993's need well-balanced tires/wheels.

 

They were road force balanced. Tried to wiggle wheel, No loose ball joints, even the bushings "look" ok. Tires seem to be wearing ok too.

I've measured some side to side error with a dial indicator, but if the error is too small I won't take it to a wheel repair place. I only want to fix a wheel if it needs it.